runtime error copying oids field

[Zhihong Yu]

Hi,
In our testPgRegressTrigger test log, I saw the following (this was for a
relatively old version of PG):

197859  [ts-1]
 ../../../../../../src/postgres/src/backend/commands/indexcmds.c:1062:22:
runtime error: null pointer passed as argument 2, which is declared to
never be null
197860  [ts-1]
 /opt/yb-build/brew/linuxbrew-20181203T161736v9/include/string.h:43:28:
note: nonnull attribute specified here
197861  [ts-1]       #0 0xacbd0f in DefineIndex
$YB_SRC_ROOT/src/postgres/src/backend/commands/../../../../../../src/postgres/src/backend/commands/indexcmds.c:1062:4
197862  [ts-1]       #1 0x11441e0 in ProcessUtilitySlow
$YB_SRC_ROOT/src/postgres/src/backend/tcop/../../../../../../src/postgres/src/backend/tcop/utility.c:1436:7
197863  [ts-1]       #2 0x114141f in standard_ProcessUtility
$YB_SRC_ROOT/src/postgres/src/backend/tcop/../../../../../../src/postgres/src/backend/tcop/utility.c:962:4
197864  [ts-1]       #3 0x1140b65 in YBProcessUtilityDefaultHook
$YB_SRC_ROOT/src/postgres/src/backend/tcop/../../../../../../src/postgres/src/backend/tcop/utility.c:3574:3
197865  [ts-1]       #4 0x7f47d4950eac in pgss_ProcessUtility
$YB_SRC_ROOT/src/postgres/contrib/pg_stat_statements/../../../../../src/postgres/contrib/pg_stat_statements/pg_stat_statements.c:1120:4

This was the line runtime error was raised:

        memcpy(part_oids, partdesc->oids, sizeof(Oid) * nparts);

>From RelationBuildPartitionDesc we can see that:

        if (nparts > 0)
        {
                PartitionBoundInfo boundinfo;
                int                *mapping;
                int                     next_index = 0;

                result->oids = (Oid *) palloc0(nparts * sizeof(Oid));

The cause was oids field was not assigned due to nparts being 0.
This is verified by additional logging added just prior to the memcpy call.

I want to get the community's opinion on whether a null check should be
added prior to the memcpy() call.

Cheers